1. Field of the Invention
The instant invention relates to multilayered structures comprising a substrate layer and a polymeric composite layer, secured to each other without a separate adhesive coating. The substrate may be a metal, e.g. aluminum, or a polymer film, e.g. a polyamide or a polyolefin film, or another rigid or flexible material. Multilayered structures comprising a metal substrate may have use in the architectural, automotive, and aircraft fields. Multilayered structures comprising a polymer film substrate may have use in packaging applications.
2. Summary of the Art
Multilayered structures have properties that are many times not obtainable in a single layered structure. Thus laminates of metals and polymers, wherein the laminate has the strength of the metal and the resistance to corrosion and sound deadening properties of the polymer are well known. Flexible film laminates wherein properties of the individual polymer films are imparted to the laminate are also widely used. For example, laminates of polyvinylidene chloride and polyamide have the excellent resistance to transmission of gases and water vapor of the polyvinylidene chloride film and the strength, scuff-resistance and gloss properties of the polyamide film. Thus, these film laminates are useful in packaging butter, soft cheese, margarine, fresh meat, etc.
In general multilayered structures comprising at least one polymer layer are prepared by bonding or laminating the separate layers to each other by using adhesives, sealing layers etc. or heat, such as in the coextrusion of polymer films and similar direct bonding processes. The use of adhesives and sealing layers is undesirable from an economic standpoint, since generally the adhesive or sealing layer contributes nothing to the properties of the multilayer structure other than delamination resistance and requires a separate application step. (The better adhesives are often solvent-based which involves the environmental and health problems of handling solvents.)
It is also known that to obtain a multilayered structure, having resistance to delamination, by direct bonding, the incorporation of additives in the polymer layer may be required. It has been found, however, that many, if not most additives that promote the adhesion of a polymer coating to substrates such as metals and other polymers having dissimilar chemical properties are not compatible with the polymer coating. (It is well known, for example, that tackifiers and similar adhesion promoters may tend to exude to the interface of the polymer coating and the substrate over time, or upon exposure of the multilayered structure to heat and moisture, thereby adversely affecting the delamination resistance of the multilayered structure.)
It will be appreciated that the laminating or bonding of polymers to substrates, without the use of adhesives or a sealing layer, would be preferred if additives were available that promoted the adhesion of the polymer and were also compatible with the polymer.
A novel class of compounds now has become known, which compounds may be described as inorganic polymers. These compounds are described in U.S. Pat. Nos. 4,232,146; 4,235,990; 4,235,991, 4,256,872, 4,267,308; 4,276,409; 4,276,410; 4,276,411; 4,298,723; 4,299,943; 4,373,079; 4,384,981; 4,386,013; 4,390,690; 4,429,111; and 4,436,899 which are hereby incorporated by reference. These compounds may be prepared having a layered structure similar to the layered structure of zirconium phosphate. The above patents teach that these novel layered compounds have many uses. However, these layered compounds have not been disclosed as useful in promoting the adhesion of polymers to substrates.